Arrangement for communicating messages via a low-voltage electricity supply system and adapter

ABSTRACT

A PC ( 10 ) connected to a low-voltage electricity supply system ( 9 ) via a mains plug ( 11 ) and a mains socket outlet ( 12 ), into which the said plug is plugged, exchanges messages with other apparatuses via the said electricity supply system by means of signals whose frequency is between 1 MHz and 40 MHz. In order to suppress high-frequency interference signals which are generated by further apparatuses which are connected to the low-voltage electricity supply system ( 9 ) via mains plugs ( 11 ′) and further mains socket outlets ( 12 ′), arranged in local proximity to the said mains socket outlet ( 12 ), or which are produced by reflections of signals at open line ends, an adapter ( 1 ) is in each case interposed there, which adapter is plugged into the mains socket outlet ( 12 ′) and into which adapter the mains plug ( 11 ′) of the respective apparatus is plugged. The adapter ( 1 ) connects each pin of the mains plug ( 11 ′) to a socket of the mains socket outlet ( 12 ′), inductor coils which block signals in the frequency range of the message transmission being situated, however, in the phase conductor and in the neutral conductor of the adapter ( 1 ).

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/CH99/00322 which has an Internationalfiling date of Jul. 14, 1999, which designated the United States ofAmerica.

TECHNICAL FIELD

The invention relates to an arrangement for communicating messages via alow-voltage electricity supply system in accordance with the preamble ofClaim 1, and also to an adapter for use in the said arrangement.

PRIOR ART

It is known for messages such as telephone calls, faxes, digital data,etc., also to be transmitted via low-voltage electricity supply systems.For this purpose, the messages are coded and impressed on ahigh-frequency carrier signal in a known manner, e.g. by frequencymodulation. The modulated carrier signal is coupled into the low-voltageelectricity supply system by the respective transmitter and is coupledout again in the same way by the respective receiver and decoded.Message transmission systems which use an electricity supply system inthis way are described e.g. in WO-A-95/19 537.

However, high-frequency interference can arise in low-voltageelectricity supply systems as a result of various processes, whichinterference is superposed on the carrier signal, is concomitantlycoupled out and, under certain circumstances, appreciably impairs thequality of the message transmission. This makes it necessary to repeatcommunications, which entails a reduction in the data rate. Suppressingsuch interference at the receiver is often possible only with aconsiderable outlay on circuitry, or is not possible at all.

The strongest interference signals often originate from the localproximity of apparatuses participating in the message exchange. Inparticular, all kinds of apparatuses connected to the mains oftengenerate interference signals with a pronounced high-frequency componente.g. during switching processes, which signals, if they pass into themains in the vicinity of an apparatus connected for reception, reach thesaid mains with almost no attenuation and appreciably interfere with themessage reception.

In addition, reflections often occur at open line terminations. Itfrequently turns out that the length of a cable between plug andapparatus constitutes precisely a quarter of the wavelength of thecarrier signal or an odd-numbered multiple thereof. This leads,irrespective of whether or not the apparatus is switched on, toparticularly pronounced reflections which are superposed on the carriersignal. Many instances of interference which greatly impair the qualityof the message transmission pass into the electricity supply system inthis way, especially in office buildings containing numerous connectedapparatuses.

In order to protect connected apparatuses, mains filters integrated inmains plugs are known, with inductances in phase conductor and neutralconductor and capacitive coupling of the same to the earth conductorconnected to a cable screen (see e.g. U.S. Pat. No. 4,614,924), thecapacitances considerably increasing the volume of the plug, inparticular its length and also the costs. U.S. Pat. No. 5,266,055 alsodiscloses a three-pole mains plug in which only inductances are used. Inboth cases, the inductances serve only for protecting the connectedapparatus against high-frequency interference signals. For this reason,the plug is also fixedly connected to the apparatus in each case. Thelast-mentioned document also shows connecting parts which serve forsuppressing interference within an apparatus. Both in the case of themains plug and in the case of the connecting part, a short conductor—astraight conductor piece or a half-loop—is embedded in ferrite materialin each case. However, only small inductances can be realized in thisway, and they only suppress signals of very high frequency.

SUMMARY OF THE INVENTION

The invention is based on the object of specifying an arrangement of thegeneric type which is significantly improved compared with knownarrangements of the generic type in respect of its suitability fortransmitting messages, and also an adapter suitable for use in thearrangement according to the invention.

By virtue of the invention's arrangement for communicating messages viathe low-voltage electricity supply system, the latter is better adjustedto transmitting messages. Interference of the aforementioned type isintercepted or suppressed at source and kept away from the mains. Thus,in particular, the reception of messages is not impaired by virtuallyunattenuated interference from the local proximity. This appliesparticularly when the frequencies utilized for the data communicationare comparatively high. The interfering effect of cable sectionssituated between plugs and apparatuses is also suppressed and a linetermination which is favourable for the transmission response of thelow-voltage electricity supply system is produced in each case.

The suppression of interference also means that more capacity isavailable for the communication of messages, since the total permissibleinterference level—which must also include the carrier signal—is usuallylimited by legal provisions. This favourable effect is additionallyenhanced by the fact that in the case of a low interference level, aweaker carrier signal also suffices.

The adapter according to the invention affords a particularly simple andhighly cost-effective possibility for realizing the arrangementaccording to the invention. It can be constructed very compactly, inparticular it can be short, and can be fitted easily and rapidly asrequired and can likewise easily be removed again as well, with theresult that the electricity supply system can largely be kept free ofinterference. The use of inductor coils saves space and avoidssaturation effects.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below with reference todrawings which merely illustrate an exemplary embodiment. In thefigures,

FIG. 1 shows a diagrammatic illustration of the adapter according to theinvention,

FIG. 2 shows a horizontal longitudinal section through the adapteraccording to the invention,

FIG. 3 shows a section along III—III in FIG. 2,

FIG. 4 shows a section along IV—IV in FIG. 2, and

FIG. 5 shows a diagrammatic illustration of an arrangement, according tothe invention, for communicating messages.

WAYS OF EMBODYING THE INVENTION

The adapter 1 according to the invention has, in a rigid, coherenthousing 2 made of plastic, a plug 3 and, on the opposite housing wall, asocket outlet 4 directed towards the opposite side. The plug 3 comprisesthree parallel pins 5 a, b, c, of which the pins 5 a, b lie in oneplane, while the pin 5 c is arranged between the two pins 5 a, b in aslightly offset manner with respect to this plane. The plug 3 issuitable for plugging into a standard-conforming mains socket outlet.

The socket outlet 4 comprises three sockets 6 a, b, c, arranged insidethe housing 2 in a configuration corresponding to the arrangement of thepins 5 a, b, c and is thus compatible with the plug 3 and is suitablefor receiving a standard-conforming mains plug corresponding thereto.The pin 5 c is designed in one piece with the socket 6 c and a straightconnecting piece 7 arranged between the two. Consequently, the pin 5 cis electrically conductively connected to the socket 6 c not via aninductance but directly, for safety reasons—the pin 5 c, the connection7 and the socket 6 c form an earth conductor connection, with the resultthat the impedance of the connection is negligibly small.

By contrast, the pin 5 a is electrically conductively connected to thesocket 6 a via an inductor coil 8 a, which is arranged underneath thesocket 6 a and next to the socket 6 c in the housing 2. The pin 5 b isconnected to the socket 6 b via an inductor coil 8 b in the same way.The arrangement described is particularly space-saving. The pins 5 a and5 b form a phase conductor and neutral conductor connection,respectively, with the inductor coil 8 a and 8 b, respectively, and thesocket 6 a and 6 b, respectively. The inductor coils 8 a, b each have aninductance of preferably at least 10 μH, with the result that theygreatly attenuate the signals whose frequency is substantially greaterthan the mains frequency of approximately 50 Hz, in particular greaterthan 1 MHz.

By dint of the restriction to inductor coils—capacitances are dispensedwith—the adapter can not only be produced inexpensively but can also beconstructed very compactly. In particular, it is possible to avoid along structural length, which, owing to the relatively large lever offorces that possibly act, would greatly increase the risk of the adapterbreaking away or else of mains socket outlets being damaged or torn out.

In an arrangement for communicating messages which may be telephonecalls, faxes, digital data, any desired audio or video signals, interalia—via a low-voltage electricity supply system 9 (FIG. 5), which ispreferably situated within a public or private building or buildingcomplex, an apparatus participating in the exchange of messages, e.g. aPC 10, is directly connected to said mains by its mains plug 11 beingplugged into a mains socket outlet 12 thereof. Via this connection, thePC 10 is on the one hand supplied with power and, on the other hand, itexchanges messages with other apparatuses (not illustrated), which arelikewise connected to the low-voltage electricity supply system 9, viathe said connection and the said low-voltage electricity supply system.In this case, a carrier frequency which is far greater than the mainsfrequency is used, the said carrier frequency preferably being between 1MHz and 40 MHz, preferably at least 10 MHz.

Further apparatuses connected to the low-voltage electricity supplysystem 9 via mains socket outlets 12′ and mains plugs 11′ in localproximity to the mains socket outlet 12, to which the PC 10 isconnected, the said apparatuses not participating in the messageexchange, such as a printer 13, a television set 14, a terminal 15 and astereo system 16, may generate interference signals with high-frequencycomponents, e.g. during switching processes. If the said interferencesignals reach the PC 10, to which the said apparatuses are connected viashort lines associated with the low-voltage electricity supply system 9,essentially with no attenuation, they could be suppressed there onlywith very complicated measures in terms of circuitry, or even not atall, and appreciably interfere with the reception of messages, on whichthey are superposed.

For this reason, the apparatuses which are considered as sources ofinterference signals are connected to the low-voltage electricity supplysystem 9 via an adapter 1 in each case. It is preferable here for theplug 3 of the adapter 1 in each case to be plugged directly into thecorresponding mains socket outlet 12′, while its socket outlet 4receives the mains plug 11′ of the apparatus. If extension cables ordistributors are used, the adapter can also be arranged at a differentlocation. In every case, high-frequency signals emerging from the saidapparatuses, in particular those signals which lie in the aforementionedrange between 1 MHz and 40 MHz which is preferred for the exchange ofmessages, are practically completely suppressed by the inductor coils 8a, b of the adapter 1, with the result that they do not interfere withthe reception of messages at the PC 10.

The adapter 1 additionally has the effect of practically decoupling thecable between the plug and the respective apparatus for signals ofrelatively high frequency, which cable constitutes an open linetermination above all in the case of an unfavourable length and cancause appreciable interference even when the apparatus is switched off.As a result, reflections are suppressed and the sum of the interferencesignals on the low-voltage electricity supply system 9 is reducedfurther, very substantially so under certain circumstances.

The reduction of interference enables the data transmission rates to beconsiderably increased. Moreover, the intensity of the carrier signalcan be reduced, thereby making it substantially easier to comply withlegal limitations for the total level of high-frequency signals on thelow-voltage electricity supply system 9.

Various modifications of the adapter are possible within the scope ofthe invention. Thus, by way of example, it may be designed as adistributor with a plurality of socket outlets, the mutuallycorresponding sockets of the phase conductor and of the neutralconductor preferably being connected to a single inductor coil connecteddownstream of the corresponding pin. It may also be designed as anextension cable, the plug, on the one hand, and the socket outlet orelse a plurality of socket outlets, on the other hand, being arranged intwo housing parts which are connected by a three-core cable. Theinductor coils are then accommodated in one of the two housing parts ordistributed between the two. The one-part embodiment portrayed ispreferred, however, owing to its particularly compact structure and tothe fact that it is simple and clear to use—particularly if the adapteris plugged directly into the mains socket outlet in each case.

Of course, the invention can also be used analogously in low-voltageelectricity supply systems conforming to other standards, e.g. withthree phase conductors.

What is claimed is:
 1. Arrangement for communicating messages via alow-voltage electricity supply system (9) having at least one phaseconductor, a neutral conductor and an earth conductor, comprising atleast one apparatus which is suitable at least for receiving or foremitting a carrier signal for the transmission of data, the frequency ofwhich carrier signal is substantially greater than the mains frequency,and is connected to the low-voltage electricity supply system (9) via aplug that is plugged into a mains socket outlet (12), and at least oneapparatus which does not participate in the exchange of data,constitutes a possible source of interference and is connected to thelow-voltage electricity supply system (9) via a mains plug (11′) and amains socket outlet (12′), which is electrically conductively connectedto the latter, characterized in that the connection between the mainsplug (11′) of the at least one apparatus constituting a possible sourceof interference and the mains socket outlet (12′) is established via anadapter (1) having a plug (3), which is connected to the mains socketoutlet (12′) and, in particular, is plugged into the latter, and atleast one socket outlet (4), to which the apparatus is connected via aplug which is plugged into the said socket outlet, which adapter (1) hasparallel conductor connections for the individual conductors of thelow-voltage electricity supply system (9), and inductance being situatedin each of the conductor connections with the exception of the earthconductor connection.
 2. Arrangement according to claim 1, characterizedin that it is situated within a building or building complex. 3.Arrangement according to claim 1 or 2, characterized in that thefrequency of the signal for the transmission of data is between 1 MHzand 40 MHz.
 4. Arrangement according to claim 1, characterized in thatthe value of the inductance is in each case between 10 μH and 20 μH. 5.Adapter (1) for use in an arrangement according to claim 1, having, in ahousing (2), a plug (3) having at least three switching pins (5 a, 5 b,5 c) for plugging into a mains socket outlet (12′), having at least onesocket outlet (4) having sockets (6 a, 6 b, 6 c) for receiving a mainsplug (11′), the said socket outlet being arranged such that it is remotefrom the plug (3) and being compatible with the latter, each switchingpin (5 a; 5 b; 5 c) being electrically conductively connected to asocket (6 a; 6 b; 6 c), characterized in that, except for in the case ofa pin (5 c) and a socket (6 c), which are connected by a directconnection (7), an inductor coil (8 a; 8 b) is in each case situatedbetween the pin (5 a; 5 b) and the socket (6 a; 6 b).
 6. Adapteraccording to claim 5, characterized in that the connection (7) betweenthe pin (5 c) and the socket (6 c) is designed in one piece with thesame.
 7. Adapter according to claim 5 or 6, characterized in that it hasprecisely one socket outlet (4).
 8. Adapter according to claim 5,characterized in that the housing (2) is designed to be coherent andrigid.
 9. Adapter according to claims 7 and 8, characterized in that ithas in each case precisely three pins (5 a, 5 b, 5 c) and three sockets(6 a, 6 b, 6 c), and the pins (5 a, 5 b) and sockets (6 a, 6 b)connected to the inductor coils (8 a, 8 b) are arranged such that theyare in each case spaced apart from one another in one plane, and theremaining socket (6 c) is fitted between them in an offset manner withrespect to the said plane, while the inductor coils (8 a, 8 b) are ineach case situated under the sockets (6 a, 6 b), connected to them, onboth sides next to the remaining socket (6 b).
 10. Adapter according toone of claims 5 to 9, characterized in that the housing (2) is composedof plastic.